Thomson scattering diagnostics at the Globus M2 tokamak

TL;DR

This paper details the development and initial testing of Thomson scattering diagnostics for the Globus-M2 tokamak, demonstrating precise measurements of electron temperature and density, and prototyping ITER-compatible systems.

Contribution

It introduces a Thomson scattering diagnostic system for Globus-M2 with features aligned to ITER requirements, including multi-wavelength laser capabilities for reliable electron temperature measurements.

Findings

Successful measurement of electron temperature and density in plasma

Demonstration of multi-wavelength laser system for spectral calibration

First measurements in both core and scrape-off layer regions

Abstract

The paper is devoted to the Thomson scattering (TS) diagnostics recently developed for the Globus-M2 spherical tokamak and prototyping the ITER divertor TS diagnostics. The distinctive features of the system are the use of spectrometers, acquisition system and lasers that meet the base requirements for ITER TS diagnostics. The paper describes the diagnostic system that allows precise measurements of TS signals, as well as the results of the first measurements of electron temperature and density in both central region of the plasma column and scrape-off layer. The system provides measurements of electron temperature $T_{e}$ in the range of 5 eV to 5 keV and density $n_{e}$ in the range of $5{\cdot}10^{17}{\div}3.25{\cdot}10^{20} m^{-3}$. The use of two ITER-grade probing lasers of different wavelengths (Nd:YAG 1064.5 nm and Nd:YLF 1047.3 nm) allows reliable measurement of $T_{e}$ in multi-colour mode, i.e., assuming that spectral calibration is unknown.